/*没有添加弹性盒子属性*/
#main {
    border: 1px dotted #f0f;
    padding: 1em;
}
.content {
    border: 1px dotted #0ff;
    padding: 1em;
}
section {
    border: 1px dotted #f00;
    padding: 1em;
}
.content section{
	background-color: #000;
	border:10px solid #dedede;
	border:none;
	asdfasdasdfasdf
	asdfasdf
}